Method for a calcium soap grease containing a hydrocarbon wax



United States Patent NETHOD FOR A CALCIUM SOAP GREASE CQN- TAINING A HYDROCARBGN WAX Hendrik Laurens Reudink, Amsterdam, Netherlands, as-

signor to Shell Development Company, Emeryville, Calif, a corporation of Delaware No Drawing. Application. February 25, 1952 Serial No. 273,360

Claims priority, application Netherlands March 22, 1951 12 Claims. (.Cl. 252-405} This invention relates to aprocess for the preparation of calcium soap greases. More: particularly it is concerned with a process for the production of greases containing substantial amounts of wax whereby the required calcium soap content is minimized.

Two types of calcium greases are produced at the present time. These may be regarded as high temperature greases, on the one hand, and low temperature greases on the other. The first type of grease comprises calcium soaps mixed with calcium salts of low aliphatic acids such as calcium acetate. wherein. the salt and soap appear to exist in a complex relationship enabling the use of the greases made therefrom at relatively high. tem peratures. Such greases contain substantially no water. The low temperature: greases" gelled with calcium soaps contain no calcium salts for stabilization butdepend upon the presence of water to form a hydrate of the soap which in turn comprises the crystal lattice forming the basis of these' greases. This invention is concerned with the second type of grease and does not relate to calcium acetatestearatev greases and the like.

Waxes and similar substances have been added to various greases to improve properties such as high temperature performance bleeding, and other characteristics. For the most part these have been greases. gelled with soaps other than calcium but certain calcium soap greases have been prepared incorporating either macrocrystalline or microcrystalline waxes. In such greases the normal procedure has been to incorporate the wax and other grease ingredients prior to formationofi a grease structure. Under these conditions'the greases so formed have been excessively soft or have required additional components to maintain a proper grease structure. For example, such major componentsv as turpentine have: been added or additives in substantial quantities have been employed 7 such as oil-soluble wetting agents. Other materials which have: been. incorporatedv to overcome the soft character of suchgreases include; free fatty acids in amounts up tov 1.0% or wool grease in amounts up to. 4% andvegetable oils in. quantities of approximately 35%. Greasemade under. the conditions of. wax incorporation prior to grease formation require as much or more calcium soap in the final product asv is necessary in ordinary calcium. greases.

It. is an object. of the. present. invention to. proyidewatercontaining calcium greases having a reduced calcium soap content. It is another object: of this invention to provide a process for the preparation of. such greases. It is a; further object of this invention to provide. calcium greaseshaving high dropping points but reduced calcium soap requirements. Other objects will. become. apparent during the following discussion.

Now, in accordance with the present invention, it. has beenfound thata calcium soap lubricating grease can be obtained when a primary lubricating grease formed from a mineral lubricating oil and a calcium soap is mixed below its dropping point with a paraflin Wax having. a melting point above about 50 C,- The temperature is still ICC 2 further limited in that it is necessary to commingle the grease and wax at a temperature above the melting point of the wax.

It has been determined that greases prepared by the above process have a substantially reduced calcium soap requirement only when the wax is present in the final composition in an amount between about 25% and 67% by weight. Still in accordance with this invention it has been found that the incorporation of inorganic colloidal gels substantially improves thedropping point of said greases while, at the same time, the high proportion of waxes acting in cooperation with the calcium soap effectively protects the amorphous gel from coagulation due to the presence of water.

The process Essentially the. process of the present invention comprises first. forming a. normal calcium grease using a calcium soap to gel a mineral lubricating oil. Subsequently this grease, referred to herein as primary calcium lubricating grease, is cornrningled. with. a hydrocarbon wax at a temperature below the dropping point of the grease but above the. melting point of the wax. Ordinarily thisv temperature of'mixing will be between about r'oomtemperature. and. C. Preferably it is between about 20 and 60 C. However, if high temperature waxes are employed or if. especially stiff greases are utilized, it may be necessary to operate at a somewhat higher temperature above 60 C. but below about 100 C. In this case the mixture of grease and wax should be subjected to shearing at least until the mixture has been cooled to a temperature of 60 C.

A preferred process comprises heating the wax to a temperature above its melting point and thereafter mixing it by means of stirringwiththe primary calcium grease, the latter being at ordinary room temperatures (usually 20-30 C.). An essential feature of the present process comprises the presence of water in the final product. It appears to=be necessary toincorporate from about 0.3% to about 3% of water based on the final composition so as to obtain greases having optimum mechanical stability and yield. Under the conditions of this process it has been found tobe possible to form calcium grease compositions having le'ss than 10% calcium soap and preferably between about 4% and about" 7% calcium soap.

An alternative additional feature of this invention comprises the incorporation of inorganic colloidal gels; The point at which such incorporation occurs is optional but preferably is effected by incorporating the colloidal gel in lubricating oil prior to the formation of the primary calcium grease structure;

The primary calcium grease The calcium greases to be utilized in the compositions prepared according to-this inventioncomprise those containing up to about 310% by weight of calcium soaps of higher fatty acids. These. may be calcium soaps of a single fatty acid or of mixtures such as those derived from the hydrolysis of. natural fat. and. oils. Preferably the fatty acids should. contain at least 12 carbon atoms per molecule andusually willcomprise mixtures of fatty acids having from 12 to 24 carbon atoms per molecule. These acids may be either saturated or unsaturated and include such species as oleic, linoleic, linolenic, stearic, 12-hydroxy' stearic, and similar fatty acids or hydroxy fatty acids well-known for their soap-forming and grease-forming properties. It is preferred that the major proportion of the lubricating oil component of such primarygreases is a hydrocarbon oil of ordinary lubricating viscosity range. Minor amounts of modifying substance may be present to. improve properties such as. viscosity index and low temperature operating characteristics; Such minor components may comprise phosphorus containing esters including tricresyl phosphate; trioctyl phosphate; dihexyl hexane phosphonate; dihexyl benzene phosphonate; di(3,5,5-trimethylhexyl) iso-octene phosphonate; bis- [2-(dioctyl phosphono)ethyl]ether; bis[2-(dinonyl phosphono)-ethyl]ether; 1,5-pentanediol bis(dibutyl phosphate), and 1,5-pentanediol bis(dioctyl phosphate).

In addition to the use of phosphorus containing esters as minor components, other esters may also be employed, such as the esters formed between monohydric alcohols and dicarboxylic aliphatic acids. A typical member of this group is bis(2-ethylhexyl)sebacate. Furthermore, polymeric lubricants such as oxyalkylene polymers may be utilized. It is preferred that the proportion of these modifying lubricants be held to a minimum and preferably to less than about by weight of the final composition. Preferably, as stated hereinbefore, the lubricant component consists essentially of a mineral lubricating oil. The primary calcium grease should contain an amount of water at least sufiicient tov provide the grease with a suitable grease-like structure. The exact proportion of water is not pertinent to the present invention since it may be adjusted either before or after the addition of wax in order to provide the final grease composition with a water content which may vary from about 0.3% to about 3% by weight. In the absence of this water, as pointed out hereinbefore, it is substantially impossible to form suitable grease structures for use as low temperature greases.

Waxes The waxes to be incorporated in accordance with the process of this invention comprise hydrocarbon waxes having melting points above about C. and preferably between about and about C. If waxes having lower melting points are employed the final grease composition is limited in its utility due to undue softness of the composition at moderately elevated temperatures. The waxes may be either macroor microcrystalline paraffin waxes obtained in the normal manner from waxy petroleum distillates or residues or may be the waxy residues remaining from the preparation of alkenes by the cracking of heavy paraflin hydrocarbons. A special variety of wax which has been found to have a particularly effective utility comprises the high melting point wax having melting points above C. Such waxes are obtained by the fractionation of waxes from heavy lubricating oil distillates or by fractionation of residual waxes. They are usually associated with microcrystalline waxes in residual wax mixtures prior to their separation. The preferred high melting point parafiin waxes are those having a substantially unbranched or only slightly branched structure as opposed to the highly branched or cyclic structures occurring in microcrystalline waxes of the same melting point.

The final compositions of this invention comprise those having the following ingredients:

Parafiin wax 25-67% (preferably 40 55%) by weight. Calcium soap 410% (preferably 4 7%) by weight. Water 0.33% (preferably 0.5-

2%) by weight. Mineral lubricating oil Balance.

4 It has been found that certain hydrophobic active agents may be used to overcome this eifeet but for the most part these have comprised high molecular weight amines and the like. In accordance with one phase of this invention it can be demonstrated that the presence of wax substantially prolongs the life of calcium soap greases which also contain inorganic colloidal gels. The gels may be present in amounts up to about 10% by weight of the final grease composition. The type of colloidal structure suitable for use in such greases is exemplified by a typical aerogel although the usual process for preparing inorganic aerogels is not required. In order to be useful as promoters for increasing the dropping point of the subject greases, the gels should have a maximum particle size of millimicrons.

Typical gels include the metallic oxides and hydroxides as well as silicates and mixtures of these classes. Suitable species are silica, magnesia, calcium hydroxide, magnesium silicate and mixtures of magnesium silicate, silica and magnesia. It has been determined that greases containing both inorganic colloidal gels and the particular waxes of the present invention provide normal calcium greases with exceptionally beneficial properties including elevated dropping points and resistance to disintegration by the action of water. It would appear to be a cooperative action between the calcium soap and the substantial amounts of waxes present in these compositions which enable the inorganic gel to resist the deleterious action of the water component. This is especially true if the high melting point waxes referred to herein before are employed. Preferably the inorganic colloidal gels are present in an amount less than about 10% by weight of the final composition and appreciably improved dropping points may be obtained by the addition of as little as 1% by weight of the final compositions.

The examples which follow illustrate the processes of the present invention and the products thereby obtained. Examples I and II illustrate the fact that when paratfin wax is added to the base oil, before the latter has formed a grease structure with the soap, only a thick fiuid mass having no lubricating properties is obtained. On the other hand, Examples HI through VII, refer to the process according to the present invention.

Example I.-To 15 parts by weight of a mixture of commercial fatty acids, which consists of about 60% by weight of oleic acid and of about 40% by weight of stearic and palmitic acid, are added 64 parts by weight of a light mineral lubricating oil with a viscosity E =7, and 21 parts by weight of the parafiinic wax residue of a cracked mineral oil residue. This paraffin residue had a melting point of 58 C. To this mixture are added 2.2 parts by weight of calcium hydroxide (commercial product), which quantity in theory would just be sutficient to convert the fatty acids completely into the corresponding soaps. The mixture is heated in an autoclave, whilst being stirred, to a temperature of C. within half an hour. It is then kept for a further half hour at this temperature and afterwards cooled over a period of about 1 hour to 60 C. while being stirred in the same autoclave.

The product obtained is a fluid mass which does not have the structure of a lubricating grease at all. The mass is slightly acidic.

Example lI.-As the product obtained according to Example I is slightly acidic, the process embodying this example can be repeated with the same initial materials in the same weight ratio and under the same conditions, using, however, a slightly larger quantity of calcium hydroxide in order to ensure that the end product will not be acidic.

A fluid mass is again obtained which is slightly alkaline. Moreover, after a time, the calcium soap settles out.

Example III.13.5 parts by weight of the same fatty acid mixture as used in the preceding examples, 86.5 parts by weight of the mineral oil as used in the preceding examples, and 2.1 parts by weight of calcium hydroxide (commercial product) are used as initial materials. This mixture is saponified in the manner indicated in the preceding examples. Afterwards the mass is cooled, whilst being stirred, to 80 C. and 102 parts by weight of the paraflinous cracked residue, as used in the preceding examples, is then added to the primary calcium lubricating grease thus obtained. This cracked residue had previously been heated to a temperature of 70 C., at

which itwas fluid. The mixture is finally cooled to 60 C., whilst being stirred, and then left undisturbed to cool completely.

In this way, a good, rather darkly coloured, lubricating grease, having the following properties, can be obtained:

Penetration (ASTM worked) at 25C. 218 Dropping point (Ubbelohde) C 95 Fatty acid content (calculated) percent by weight 6.7

Example IV.--A calcium lubricating grease, prepared in the same way as the primary calcium lubricating grease of Example III, is placed, at room temperature in an open agitator with an amount equal to it of the same paraifinous cracked residue as used in the preceding examples.

This cracked residue had previously been heated to 70 C. and is therefore in a fluid state. The mixture of the original calcium grease and the cracked residue is stirred until the temperature falls to 40 C., a good, rather darkly coloured, lubricating grease having the following properties being obtained:

Penetration (ASTM worked) at 25 C. 220 Dropping point (Ubbelohde) C 97 Fatty acid content (calculated) percent by weight 6.7

Example V.A calcium lubricating grease, prepared in the same way as the primary calcium lubricating grease of Example III, is placed at room temperature in an open agitator and, whilst being stirred, heated to 75 C. Afterwards, again in course of stirring, an equal amount by weight of a macrocrystalline wax with a melting point of 615 C. is slowly added to it. The parafiin wax had previously been heated to 80 C. and was therefore in a fluid state. The mixture of the original calcium lubricating grease and the parafiin wax is finally stirred whilst being cooled until a temperature of 40 C. is reached.

In this way a yellowish-brown lubricating grease having the following properties is obtained:

Penetration (ASTM worked) at 25 C 177 Dropping point (Ubbelohde) C 93 Fatty acid content (calculated) percent by weight 6.7

Example VI.-A calcium lubricating grease, prepared in the same way as the primary calcium lubricating grease of Example III, is placed, at room temperature in an open agitator and heated whilst being stirred to 75 C. Afterwards, again in course of stirring, an equal amount by weight of a microcrystalline wax with a melting point of 71 C. is slowly added. The paraffin wax had previously been heated to 80 C. and is therefore in a fluid state. The mixture obtained is finally stirred again whilst being cooled until a temperature of 40 C. is reached.

In this way a Vaseline-like lubricating grease with the following properties can be obtained:

Penetration (ASTM worked) at 25 C 165 Dropping point (Ubbelohde) C 97 Fatty acid content percent by weight" 6.7

Example VII.--The composition according to Example III can be modified by the incorporation of 2-8% by tact of 'the finalcomposition with water even upon prolonged contact.

I claim as my invention:

1. In a process for the preparation of water-containing grease compositions having a low soap content containing calcium soaps of higher aliphatic monocarboxylic acids as the'sole soap gelling agent, the step comprising commingling a pre-formed calcium soap grease and a hydrocarbon wax at a temperature above the melting point of the wax, said wax having a melting point above 50 C. and being present in an amount from about 25% to about 67% by weight of the final grease composition, said composition containing from about'0.3% to about 3% by weight of water, the temperature of said compositions being maintained at all times below the dropping point of the grease.

2. In a process for the preparation of water-containing grease compositions having a low soap content containing calcium soaps of higher aliphatic :monocarboxylic acids as the sole soap gelling agent, the step comprising commingling a pro-formed calcium soap grease and a hydrocarbon wax at a temperature above the melting point of the wax, said wax having a melting point above 50 C. and being present in an amount from about 40% to about 55% by weight of the final grease composition, said composition containing from about 0.3 to about 3% by weight of water, the temperature of said compositions being maintained at all times below the dropping point of the grease.

3. In a process for the preparation of water-containing grease compositions having a low soap content containing calcium soaps of higher aliphatic monocarboxylic acids as the sole soap gelling agent, the step comprising commingling a pre-formed calcium soap grease and a hydrocarbon wax at a temperature above the melting point of the wax, said wax having a melting point above 50 C. and being present in an amount from about 25% to about 67% by weight of the final grease composition, said composition containingfrom about 0.5% to about 2% by weight of water, the temperature of said compositions being maintained at all times below the dropping point of the grease.

4. In a process for the preparation of water-containing grease compositions having a low soap content containing calcium soaps of higher aliphatic monocarboxylic acids as the sole soap gelling agent, the step'comprising commingling a pro-formed calcium soap grease and a hydrocarbon wax at a temperature above the melting point of the wax, said wax having a melting point from about 55 C. to about 75 C. and being present in an amount from about 25% to about 67% by weight of the final grease composition, said composition containing from about 0.3% to about 3% by weight of water, the temperature of said compositions being maintained at all times below the dropping point of the grease.

5. In a process for the preparation of water-containing grease compositions having a low soap content containing calcium soaps of higher aliphatic monocarboxylic acids as the sole soap gelling agent, the step comprising commingling a pro-formed calcium soap grease and a hydrocarbon wax at a temperature between about 60 C. and about C. and subjecting said composition to shearing action while it cools to a temperature below about 60 C., said wax having a melting point above about 50 C. and being present in an amount from about 25% to about 67% by weight of the final grease composition, said composition containing from 0.3% to about 3% by weight of water, the temperature of said compositions being maintained at all times below the dropping point of the grease.

6. In a process for the preparation of water-containing grease compositions having a low soap content containing calcium soaps of higher aliphatic monocarboxylic acids as the sole soap gelling agent, the step comprising commingling a pre-formed calcium soap grease having a temperature of between C. and C. and a hydrocarbon wax at a temperature above the melting point of said wax, the latter having a melting point above about 50 C. and being present in an amount from about 25% to about 67% by weight of the final grease composition, said composition containing from about 0.3% to about 3% by weight of water, the temperature of said compositions being maintained at all times below the dropping point of the grease.

7. In a process for the preparation of Water-containing grease compositions having a low soap content containing calcium soaps of higher aliphatic monocarboxylic acids as the sole soap gelling agent, the step comprising commingling a pre-formed calcium soap grease and a hydrocarbon wax at a temperature above the melting point of the wax, said wax having a melting point above 50 C. and being present in an amount from about 25% to about 67% by weight of the final grease composition, said composition containing from about 0.3% to about 3% by weight of water, the calcium soap content being less than about 10% by weight of the composition but in an amount at least suflicient to provide said composition with a grease structure, the temperature of said compositions being maintained at all times below the dropping point of the grease.

8. In a process for the preparation of water-containing grease compositions having a low soap content containing calcium soaps of higher aliphatic monocarboxylic acids as the sole soap gelling agent, the step comprising commingling a pre-formed calcium soap grease and a hydrocarbon wax at a temperature above the melting point of the wax, said wax having a melting point above 50 C. and being present in an amount from about 25 to about 67% by weight of the final grease composition, said composition containing from about 0.3% to about 3% by weight of water, the calcium soap content being between about 4% and about 7% by weight of the final composition, the temperature of said compositions being maintained at all times below the dropping point of the grease.

9. In a process for the preparation of water-containing calcium stearate grease compositions having a low calcium stearate content containing calcium soaps of higher aliphatic monocarboxylic acids as the sole soap gelling agent, the step comprising commingling without further heating a pre-formed calcium stearate grease and 8 a hydrocarbon wax at a temperature above the melting point of the wax, said wax having a melting point above C. and being present in an amount from about 25% to about 67% by weight of the final grease composition, said composition containing from about 0.3% to about 3% by weight of water.

10. In a process for the preparation of water-contain ing grease compositions having a low soap content containing calcium soaps of higher aliphatic monocarboxylic acids as the sole soap gelling agent, the step comprising commingling without destroying the grease structure a pre-formed calcium soap grease and a hydrocarbon wax at a temperature above the melting point of the wax, said wax having a melting point of about 61.5 C. and being present in an amount of about 50% by weight of the final grease composition, said composition containing from about 0.3% to about 3% by weight of water.

11. A grease composition prepared according to the process of claim 1 said pre-formed grease consisting essentially of a gelling proportion of calcium soaps of higher aliphatic monocarboxylic acids and a mineral lubricating oil, the soap content of the final wax-containing grease being between 4% and 10% by weight.

12. A grease composition prepared according to the process of claim 2 said pre-formed grease consisting essentially of a gelling proportion of calcium soaps of higher aliphatic monocarboxylic acids and a mineral lubricating oil, the soap content of the final wax-containing grease being between 4% and 10% by weight.

References Cited in the file of this patent UNITED STATES PATENTS 1,871,864 Sullivan et al. Aug. 16, 1932 2,113,754 Zimmer et al. Apr. 12, 1938 2,197,263 Carmichael et al. Apr. 16, 1940 2,408,385 Flood Oct. 1, 1946 2,442,828 Smith et al June 8, 1948 2,444,357 Maguire June 29, 1948 2,513,680 Schott et al. July 4, 1950 2,534,053 OHalloran Dec. 12, 1950 2,538,394 Schott et al Jan. 22, 1952 2,583,605 Sirianni Jan. 29, 1952 2,607,735 Sproule et a1 Aug. 19, 1952 

1. IN A PROCESS FOR THE PREPARATION OF WATER-CONTAINING GREASE COMPOSITIONS HAVING A LOW SOAP CONTENT CONTAINING CALCIUM SOAPS OF HIGHER ALIPHATIC MONOCARBOXYLIC ACIDS AS THE SOLE SOAP GELLING AGENT, THE STEP COMPRISING COMMINGLING A PRE-FORMED CALCIUM SOAP GREASE AND A HYDROCARBON WAX AT A TEMPERATURE ABOVE THE MELTING POINT OF THE WAX, SAID WAX HAVING A MELTING POINT ABOVE 50*C. AND BEING PRESENT IN AN AMOUNT FROM ABOUT 25% TO ABOUT 67% BY WEIGHT OF THE FINAL GREASE COMPOSITION SAID COMPOSITION CONTAINING FROM ABOUT 0.3% TO ABOUT 3% BY WEIGHT OF WATER, THE TEMPERATURE OF SAID COMPOSITIONS BEING MAINTAINED AT ALL TIMES BELOW THE DROPPING POINT OF THE GREASE. 